About Rationally Speaking

Rationally Speaking is a blog maintained by Prof. Massimo Pigliucci, a philosopher at the City University of New York. The blog reflects the Enlightenment figure Marquis de Condorcet's idea of what a public intellectual (yes, we know, that's such a bad word) ought to be: someone who devotes himself to "the tracking down of prejudices in the hiding places where priests, the schools, the government, and all long-established institutions had gathered and protected them." You're welcome. Please notice that the contents of this blog can be reprinted under the standard Creative Commons license.

Thursday, February 21, 2008

One more example of how science works

The news keeps coming in, and examples of how real science works (as opposed to make believe creationism or so-called intelligent design) are beginning to get so numerous that it is hard to imagine people capable of reading newspaper articles are still capable of denying evolution. Last week, for instance, a spectacular discovery was published in Nature magazine, a finding that has resolved a long-standing question about the evolution of bats.

Darwin listed the problem as one of the great mysteries of evolution he was not able to address in “The Origin of Species”: how did bats originate from terrestrial ancestors? The modern version of the conundrum hinged, until last week, on whether flight or echolocation (the amazing ability of bats to generate a sonar-like pulse to orient themselves and locate preys) came first. For decades biologists have been arguing in favor of either the flight-first or the echolocation-first hypothesis. There were reasonable arguments on either side: we know of the existence of some modern shrews that have a rudimentary system of echolocation, lending credence to the possibility that echolocation came first, as a means to locate prey on the ground first, and perhaps in arboreal environments later.

On the other hand, in the 1980s, studies showed that terrestrial echolocation is extremely expensive metabolically, and that it can be sustained easily by the animal only in flight (because the same muscles used to power flight also generate the sound waves, at little additional energetic cost). Still, the problem remained unsolved because all fossil bats known (until last week) were clearly capable of echolocation (we can tell from the size of the cochlea inside their ears) and capable of powered flight (as judged by their skeletal structure).

But that is what’s truly amazing about science: you can literally wake up one morning and find that someone has figured out the answer to a question that has vexed people for decades, sometimes centuries. In this instance, work by N.B. Simmons and collaborators has unearthed two specimens of bats that are 52.5 million years old (as close as we’ve gotten so far to the time scientists think bats originated from terrestrial ancestors). The stupendous fossils clearly show that the animals were capable of flight, but their cochleae simply could not have allowed echolocation. Mystery solved: flight came first!

But, the sensible reader might say, how did bats start to fly in the dark without echolocation? Wouldn’t they be literally bumping into things in the night? The currently favored hypothesis is that bats began to fly as diurnal animals, and were eventually pushed into a nocturnal habit by increased competition from birds, after the dinosaurs’ demise 65 million years ago. This hypothesis makes a very specific prediction about the structure of the eye sockets of early bats, which are expected to be different between diurnal and nocturnal animals. Unfortunately, the two specimens studied by Simmons and colleagues have their upper skulls crushed, so that it isn’t possible to reconstruct the eye sockets.

Science solved a mystery, only to run immediately into a new one. But of course, next week, or next year, someone may find a new fossil that will settle this question too, and so on and so forth. Now, when was the last time a creationist discovered something that settled a scientific dispute? Didn’t think so.

11 comments:

Wow, that is very interesting! I forgot that bats could see in the light. I think it makes the most sense that they would have been flying first. And if the daytime was too competitive, then that would quickly lead to bats getting better and better at finding their way around in the dark, which developed into echolocation.

m "The stupendous fossils clearly show that the animals were capable of flight, but their cochleae simply could not have allowed echolocation. Mystery solved: flight came first!

But, the sensible reader might say, how did bats start to fly in the dark without echolocation? "let us not forget..Humans also have been known to opportunistically use echolocation, so I am not positive that this is as exceptional of a leap in evolutionary traits as you think it is. The ability of some people and animals to interpret or get clues from their surrounding sensory input is not that big of a mystery. It is very common that if one skill is lost (even in one lifetime) other skills are heightened and used by the person and or animal to survive.

I heard a story of a blind boy who uttered "clicks" with his mouth to figure out where he was and if he were about to run into something. And he could do this very proficiently. I believe he even skateboarded using this "trick". And so the size of the various components of his ears may or may not have anything thing to do with it. The question is, will he pass this ability on to his children? Probably not. So I seriously doubt that what we see in the case to which you refer has a single thing evolutionary about it.

btw, has anyone ever been to Carlsbad Caverns? THERE YOU CAN see like bazzilions of bats.

Oh my goodness, really fun stuff!!!

If you haven't gone, do go sometime. It is cool, clammy smelly and you totally feel like you are taking a journey to the center of the earth!

"..But, the sensible reader might say, how did bats start to fly in the dark without echolocation? "

paulThat was Massimo's question. I should have separated the comments better.

My point was that any trait that can be readily be developed in one life time, or less, has probably little or nothing to do with evolution.

in spite of increased technology, i think human brains are really not as good, capable or inventive as they use to be. Trade-offs, that is the loss of one sensory ability and therefore the picking up of an enhanced a skill on another level are really going to become an increasingly frustrated process, especially if you truly believe that it takes 50 million years to improve an ear or other type of cognitive ability.

It is a view, I think, that seems pro-evolution on one front and very anti-evolution on the other. But you, of course, are entitled to it.

This young fella is a really interesting case study of certain types of abilities emerging instantly. My husband and I watched his bio one evening a few weeks ago. Derek is blind, autistic and retarded but he can play complicated musical pieces with only one hearing. And basically acquired this ability instantly.

My husband can also play pieces generally that he has only heard once, but it ain't such a big deal since he is neither blind, retarded or autistic. :) Even so, those who do music with with him have suggested that he is savant-like in his abilities.

Maybe some things in life just are what they are - a miracle. And maybe it is quite okay to just believe that.

"Clicks...The question is, will he pass this ability on to his children? Probably not. So I seriously doubt that what we see in the case to which you refer has a single thing evolutionary about it."

What a Lamarkian thing to say, Cal. (or is that Lamarkable? )

Of course the Echolocation wasn't irreducibly complex. The oral capacity for clicking was coupled with the auditory capacity to hear some things to make a better mousetrap, i.e. know where you are going without being able to see.

The capacity was there, the evolution was because of the selective pressure to get around accurately in the shadows and then in the dark.

It's a good example of using the parts of the mousetrap which were already there...for another function, motion without vision, selected over time, not all at once.

Lamarck was discredited because his ideas actually did not work and were not even sensible. I am talking about adaptations that do in fact truly work in less than one generation.

No comparison there. And who are you, btw?

Keep in mind that Darwin was supportive of Lamarck: http://www.ucmp.berkeley.edu/history/lamarck.html"..Today, the name of Lamarck is associated merely with a discredited theory of heredity, the "inheritance of acquired traits." However, Charles Darwin, Lyell, Haeckel, and other early evolutionists acknowledged him as a great zoologist and as a forerunner of evolution. Charles Darwin wrote in 1861:

Lamarck was the first man whose conclusions on the subject excited much attention. This justly celebrated naturalist first published his views in 1801. . . he first did the eminent service of arousing attention to the probability of all changes in the organic, as well as in the inorganic world, being the result of law, and not of miraculous interposition."

As if the existence of the "law" itself could not somehow be a miracle.

As a matter of fact I do think Darwin lifted half of his conclusions from Lamarck and the other from Mendel. But the two botanists were very different in their conclusions and mechanistic routes, so making an effort to blend the competing views takes a certain amount of linguistic trickery. Possibly the only thing that Darin was literally proficient at.

And if the latter half of this historical account on Lamarck is accurate, Massimo is basically suggesting Lamarckism too. I am not.

From the same Berkley History page: "While the mechanism of Lamarckian evolution is quite different from that proposed by Darwin, the predicted result is the same: adaptive change in lineages, ultimately driven by environmental change, over long periods of time. It is interesting to note that Lamarck cited in support of his theory of evolution many of the same lines of evidence that Darwin was to use in the Origin of Species. Lamarck's Philosophie zoologique mentions the great variety of animal and plant forms produced under human cultivation (Lamarck even anticipated Darwin in mentioning fantail pigeons!); the presence of vestigial, non-functional structures in many animals; and the presence of embryonic structures that have no counterpart in the adult. Like Darwin and later evolutionary biologists, Lamarck argued that the Earth was immensely old. Lamarck even mentions the possibility of natural selection in his writings, although he never seems to have attached much importance to this idea.

It is even more interesting to note that, although Darwin tried to refute the Lamarckian mechanism of inheritance, he later admitted that the heritable effects of use and disuse might be important in evolution. In the Origin of Species he wrote that the vestigial eyes of moles and of cave-dwelling animals are "probably due to gradual reduction from disuse, but aided perhaps by natural selection." Lamarckian inheritance, at least in the sense Lamarck intended, is in conflict with the findings of genetics and has now been largely abandoned -- but until the rediscovery of Mendel's laws at the beginning of the twentieth century, no one understood the mechanisms of heredity, and Lamarckian inheritance was a perfectly reasonable hypothesis."

Therefore Mendelism is the only accurate view of heritable traits and it is not an evolutionarily supported one.

As a matter of fact I do think Darwin lifted half of his conclusions from Lamarck and the other from Mendel.

Care to read the text you yourself pasted to you comment? Borrowing Lamarck, sure. But from Mendel? Read a bit more about it. Mendel published his stuff SIX years AFTER Darwin's book was out. And nobody gave Mendel's work much attention until 1900 anyway. How could Darwin lift anything from a work didn't exist, and of which he most surely wasn't aware of anyway even later?

Therefore Mendelism is the only accurate view of heritable traits and it is not an evolutionarily supported one.

I don't know what you mean by "Mendelism", since there are a few different conclusions from his paper... Whatever the conclusion anyway, where on the warming Earth did you get the absurd idea that it is "not evolutionarily supported"? Unless you went into a coma some 60 or 70 years ago and woke up just last week, in which case: time to catch up...

Now it appears that we have two anti-evolution "authorities" who are posting as anonymous. Could the anonymous #2 who is not Cal come up with a handle so we know what to call you? That way we know who to address comments to. If not it will just be "Stupid", but I would rather not resort to that. But for now.

Stupid said:"Therefore Mendelism is the only accurate view of heritable traits and it is not an evolutionarily supported one."

Hey Stupid,Maybe you ought to do a little more research into evolutionary theory, and start by looking into what is called the "New Synthesis". Evolution does not rest on the authority of Darwin, but on the utility of his ideas that are illuminated by later scientific developments.